Prosthetic devices are often required for repairing defects in bone tissue in surgical and orthopedic procedures. Prostheses are increasingly required for the replacement or repair of diseased or deteriorated bone tissue in an aging population and to enhance the body's own mechanism to produce rapid healing of musculoskeletal injuries resulting from severe trauma or degenerative disease.
Autografting and allografting procedures have been developed for the repair of bone defects. In autografting procedures, bone grafts are harvested from a donor site in the patient, for example from the iliac crest, to implant at the repair site, in order to promote regeneration of bone tissue. However, autografting procedures are particularly invasive, causing risk of infection and unnecessary pain and discomfort at the harvest site. In allografting procedures, bone grafts are used from a donor of the same species but the use of these materials can raise the risk of infection, disease transmission, and immune reactions, as well as religious objections. Accordingly, synthetic materials and methods for implanting synthetic materials have been sought as an alternative to autografting and allografting.
Synthetic prosthetic devices for the repair of defects in bone tissue have been developed in an attempt to provide a material with the mechanical properties of natural bone materials, while promoting bone tissue growth to provide a durable and permanent repair. Knowledge of the structure and bio-mechanical properties of bone, and an understanding of the bone healing process provides guidance on desired properties and characteristics of an ideal synthetic prosthetic device for bone repair. These characteristics include, but are not limited to: bioresorbability so that the device effectively dissolves in the body without harmful side effects; osteostimulation and/or osteoconductivity to promote bone tissue in-growth into the device as the wound heals; and load bearing or weight sharing to support the repair site yet exercise the tissue as the wound heals to promote a durable repair.
Materials developed to date have been successful in attaining at least some of the desired characteristics, but nearly all materials compromise at least some aspect of the bio-mechanical requirements of an ideal hard tissue scaffold.